In many wireless networks using channels in the 60 GHz range, line of sight signal paths are the predominant signal paths because the signals are severely attenuated. This makes such networks well-suited for efficient spatial reuse, and are therefore good candidates for multi-user multiple input multiple output (MU MIMO) techniques. However, once beam-forming training has been completed, and highly directional links have been established, conventional protocols established for omni-directional communications may be inadequate.